This research project is designed to analyze the apparent reinnervation of the partially deafferented hippocampal formation by sympathetic noradrenergic neurons undergoing regenerative or collateral sprouting as a result of fimbrial-fornix transection. The principal objectives of this program are to determine (1) if synaptic contacts are formed with neural elements, (2) what the location and frequency of such anomalous synaptic contacts are relative to those of the normal noradernergic innervation, and (3) if the distribution of anomalous terminals can be modified by more extensive deafferentiation in the adult or by similar damage in neonatal rats. This will be accomplished using electron microscopy in conjunction with permanganate fixation, 5-hydroxydopamine pretreatment (to reveal small granular vesicles in the CNS), or autoradiography of exogenous (3H) noradrenaline; and using fluorescent histochemistry on brains with simultaneous hippocampal transections and entorhinal cortex lesions in adult and newborn animals.